The present invention relates to a printing method in a video printer and, in particular, a high-speed printing method for efficiently reducing a printing time needed to print one document line in a color video printing apparatus having a line memory, thereby enabling a high-speed printing of a document.
In general, it has been known that three elementary colors of Cyan, Magenta and Yellow for printing a given document image in a color video printer may be obtained from a given color conversion process of the so-called, three primary colors Red, Green and Blue of a light ray. The former three colors are mixed to each other to produce a desired color image in the color video printer. That is, the latter three primary colors Red, Green and Blue are respectively, or compositively, converted to the former three elementary colors Yellow, Magenta and Cyan to obtain a desired number of color gradation, for example, 256 gradations of representing a given color image.
In a conventional printing method, for the color video printer utilizing 256 gradations to print one document line from a line memory, a total of 256 times of thermal print head operations are required to complete printing of one line, which operations have no particular reference to the gradations and are carried out either in a thermal or in a non-thermal state. In this case, the total 256 times of thermal print head operations should be always carried out irrespectively of a gradation characteristic in the corresponding line, which inevitably may lead to an unnecessarily long printing time on a color video printer.
For example, when making a print for a given video image provided from a television screen to a color video printer, all of the three elementary colors Yellow, Magenta and Cyan may not be used in their respective maximum degree of thickness. Hence, there is would be no need to have a thermal print head of the color video printer operating 256 times for each color representation.
It is therefore an object of the present invention to provide a high-speed printing method capable of considerably reducing a printing time consumption in a color video printer by having at least one line memory.
According to one aspect of the invention, the method may be achieved by limiting a frequency of thermal operation in a thermal printing device of a printer below the maximum gradation number of a print line.
According to another aspect of the invention, the method preferably includes a method of controlling printing in a color video printer having at least one line memory provided with a plurality of gradation data corresponding to a respective color component, the line memory for receiving at least one line data indicative of a given color image from a video memory, the method further comprising the steps of:
searching the largest value of one line data from the line memory;
designating the largest value as a maximum value of heating gradation relative to the one line data; and
terminating one cycle of printing operation for the one line data when reaching the maximum value of the heating gradation, irrespectively of a total heating gradation number.